1. Field of the Invention
The present invention relates generally to wireless charging, and more particularly, to an apparatus and method for performing wireless charging, to supply power, between electronic devices.
2. Description of the Related Art
A wireless charging technique, which is a wireless power technique, refers to a technique which enables a battery of an electronic device to be automatically charged when the electronic device is put on a charging pad without connecting it to an additional charger. Generally, wireless electric toothbrushes and wireless electric shavers are charged using the wireless charging technique and this technique is well-known. The wireless charging technique applied to such products has attracted attention because it enhances waterproof functionality and improves portability due to a wired charger becoming unnecessary.
The wireless charging technique may be broadly categorized into an electromagnetic induction type which uses coils, a wireless power transmission type which converts electric energy into microwaves for transmission, and a resonance type which uses a resonance phenomenon.
The electromagnetic induction technique works by transmitting power between a primary coil and a secondary coil. When moving a magnet around a coil, a current is induced and electricity is generated. That is, a transmitter generates a magnetic field and a receiver generates energy on behalf of the magnet. The electromagnetic induction technique has the advantage of efficient high-energy transmission. The electromagnetic induction technique has been put to practical use in the greatest number of areas and has been applied to a variety of electronic devices.
The resonance technique works by wirelessly transmitting power using a resonance-type power transmission principle even though a device is away from a charger by a few meters. The resonance technique uses a physical concept in which, for example, if a tuning fork vibrates, a wine glass near the tuning fork also vibrates at the same frequency. In the resonance technique, power is wirelessly transmitted by resonating electromagnetic waves containing electric energy instead of resonating sound.
The wireless power transmission technique works by wirelessly transmitting power by radio frequency/microwave radiation. The wireless power transmission technique is a new concept in power transmission in which power energy is converted for transmission into microwaves which are advantageous for wireless transmission.
Many electronic devices utilizing one of the various power transmission techniques have come to market. However, a use range of the power transmission technique employed up to now is limited to certain electronic devices, such as wireless electric shavers or a wireless electric toothbrushes, having a short distance from their chargers. Recently, as wireless charging techniques have been increasing in demand even in electronic devices, such as mobile terminals, for which mobility is important, a technique for wirelessly charging electronic devices irrespective of their locations has been demanded.